A conventional electrical power switch device (also called a “breaker”) for shutting off three-phase AC electric power in a power station of an industrial facility includes a switch box includes three power supply or “line” stabs (terminals) on one side, usually on a top side (the line side), and three power outlet or “load” stabs on another side, usually the bottom side (the load side), of the device, with a breaker handle that electrically connects and disconnects the three line side breaker stabs to the three load side breaker stabs when the switch is thrown between connect and disconnect positions.
FIGS. 1 and 2 show a conventional electrical power switch device 100 mounted on support structures 50,52. The industrial facility employing low voltage electrical power (600V and lower) has a power station with three lines of power supply, terminating in three power supply or “line side” bussings 12,14,16. The three line side bussings 12,14,16 are usually in a fixed, spaced-apart position upon a fixed structure of the facility. The lateral positions of the three line side bussings 12,14,16 are typically predetermined and fixed.
In the illustrated embodiment, the first line side bussing 12 includes a pair of nested, C-shaped conductive members 12a,12b, with outer conductive member 12a having an inner surface and the inner conductive member 12b having an outer surface. Likewise, second and third line side bussings 14 and 16 have outer conductive members 14a,16a having an inner contact surface and the inner conductive member 14b,16b having an outer contact surface. The inner and outer contact surfaces of the bussings lie in common planes, respectively.
The power switch device 100 (P frame breaker) includes a top end 102 and a bottom end 104, and a switch arm (not shown). Three spaced-apart line side breaker stabs 112,114,116 extend in rigidly fixed positions from the top end 102, each with opposed outer-facing and inner-facing surfaces that lie in respective common planes. Three spaced-apart load side breaker stabs 122,124,126 extend in rigidly fixed positions from the bottom end 104.
Each of the line side breaker stabs 112,114,116 are placed into electrically conductive position with the line side bussings 12,14,16, by inserting the line side breaker stabs between the confronting contact surfaces of the inner and outer conductive members of the line side bussings 12,14,16, and securing them tightly together to minimize electrical resistance between the line side bussings and the line side breaker stabs. To illustrate, FIG. 2 shows the middle line side breaker stab 114 positioned in conductive contact with the line side bussing 14, between the confronting faces 15a and 15b, respectively, of line side bussing conductive members 14a and 14b. Each line side bussing 12,14,16 has a centered opening 18 through the outer surface 13,15,17, through which a bolt 60 and nut 61, or other fixture, can be passed, which also passes through a similar centered opening 218 in the line side breaker stabs, to secure the line side bussings 12,14,16 to the respective three line side breaker stabs 112,114,116 of the switch box 100.
Similarly, each lower load side breaker stab 122,124,126 is placed into electrically conductive position with the respective load side bussings 22,24,26. In FIG. 2, the middle load side breaker stab 124 is positioned into conductive contact with the load side bussing 24. In an alternative securement arrangement, the load side breaker stabs 122,124,126 are secured flush against the outer surface of the load side bussings 22,24,26, and secured tightly together with a bolt 60 and nut 61.
The line side bussings and the load side bussings of the facility are secured in a fixed position within the support structure of the facility, and usually cannot be easily moved or repositioned. The line side bussings and the load side bussings are typically made of a copper bar material, to minimize resistance to the flow of electrical current. Similarly, the line side breaker stabs and the load side breaker stabs of the switch box are typically made of a copper bar material, and the confronting surfaces of the bussings and stabs are smooth and planar in order to minimize resistance to the flow of the electrical current.
When it becomes necessary, the conventional switch box 100 may be replaced by an updated switch box, which may not have the same size and dimensions as the conventional switch box 100. In such a situation, the installation of the updated switch box to the support structure 50,52 can be troublesome if the line side breaker stabs and load side breaker stabs of the updated switch box do not align with the line side bussings and load side bussings.